The present invention relates to a method and a device for protecting a printed board against overcurrents by mounting thereon a printed board fuse which will interrupt the current in case of overcurrents.
From, for example, EP-A1 0 270 954 there is previously known a chip-type fuse which may be used mounted on and connected to a printed circuit board/printed board. Said chip-type fuse comprises an insulating member, such as an insulating substrate having a pair of metallic electrodes of thin-film type disposed thereon, between which a current sensitive conductor is connected. Should an overcurrent pass through the fuse, the conductor will melt and the current will be interrupted. In order to prevent, in case of the conductor melting because of an overcurrent, a generated metal vapour from being set free and spreading and also to prevent arc discharge, the conductor is coated with a protective silicone resin film. Despite the small size of the fuse, the insulating member/substrate permits high current intensities. For increased sensitivity, the chip-type fuse may optionally be provided with trimmed portions which would more easily melt in case of an overcurrent.
From FR-A 2 053 881 there is previously known a similar fuse for printed circuits/printed boards. It is made according to the technique for printed circuits or rather by means of a method for analogue circuits such as metal coating, electroplating or attachment of a metallic film. The fuse is characterized in that the conductive current sensitive circuit contains a plurality of spaced apart constricted areas adjacent extended conductive surfaces. In the case of a temperature rise in the constricted areas, the substrate will not be affected since the constricted areas are located adjacent the extended conductive surfaces, which are exposed to the air so that the heat may be dissipated.